(1) Field of the Invention
The present invention relates to a method of manufacturing an organic electroluminescence device and a method of setting a laser focal position.
(2) Description of the Related Art
Conventionally, in an organic electroluminescence (hereinafter, referred to as an organic EL) device including an organic layer interposed between an anode and a cathode, there is a case where a short circuit is caused between the anode and the cathode due to attachment or mixture of a conductive foreign substance during the manufacturing process. In this case, there is a method of repairing the shorted portion by irradiating the shorted portion with laser (see, for example, Patent References 1 to 4: Japanese Unexamined Patent Application Publication No. 2004-227852; Japanese Unexamined Patent Application Publication No. 2003-178871; Japanese Unexamined Patent Application Publication No. 2005-276600; and Japanese Unexamined Patent Application Publication No. 2008-235177).
Patent Reference 1 discloses detecting a conductive foreign substance attached to an organic EL device and irradiating an organic layer in a region surrounding this foreign substance. This allows insulating the organic layer which is interposed between the anode and the cathode in the organic EL device and to which the foreign substance is attached, so as to form the region into a high resistance region, thus solving the short circuit between the anode and the cathode caused by the foreign substance.
Patent Reference 2 discloses irradiating the portion in which the short circuit is caused by the foreign substance, prior to forming a protection film above the anode and the cathode. This solves to deform or burns off the foreign substance, so as to solve the short circuit between the anode and the cathode.
Patent Reference 3 discloses cutting off, so as to physically separate a part of a cathode including a short circuit between the anode and the cathode, from another portion of the cathode without short circuit, thus solving the short circuit caused between the anode and the cathode by the foreign substance.
Patent Reference 4 discloses irradiating a luminescence defective spot in an organic EL device with a laser such as a femtosecond laser, thus forming a missing portion with which to solve the short circuit.
By the methods of solving the short circuit as disclosed in Patent References 1 to 4 described above, a short-circuit state between the anode and the cathode can be solved. However, also assumed is the case where the irradiated laser is scattered around the shorted portion, and this leads to deformation or alteration of each normal laminated layer included in the organic EL device, causing an opposite effect of decreased luminance efficiency and shortened life of the organic EL device. Accordingly, for the organic EL device having a microstructure, it is important to irradiate the shorted portion with a laser without damaging a periphery of the shorted portion.
For the laser irradiation described above, Patent Reference 5 (Japanese Patent No. 3154176) discloses a method of efficiently irradiating an irradiation target point with a laser. The literature discloses a focal position control method for a laser welder that is capable of detecting the laser light reflected from the welded portion and automatically adjusting the focus based on the intensity thereof. Specifically, the focus control is to measure the intensity of the laser light reflected from the welded portion and minimize the intensity of the reflected laser light by controlling a height of a drive stage based on a predetermined adjustment algorithm such that the result of the measurement does not exceed a threshold. In other words, the method is to irradiate a single-layer material such as a welding material with a laser so as to obtain reflected laser light, and focus the laser on the welded portion by monitoring the reflected laser light. This allows controlling the focal position of the laser beam with respect to the welded object constantly at an optimum position, thus achieving stabilized welding quality and improved efficiency.